Alkyne copolycyclomerizations of aromatic diynes 2,7-bis(4-ethynylphenylethynyl)-9,9-diliexylfluorene (1) and I 4-bis(4-ethynylphenylethynyl) benzene (11) with an aliphatic moncyne 1-dodecyne (A) were effected by CPCO(CO)(2)-hv in THF, producing hyperbranched poly(aryleneethynylene)s 1 and 2) Of high molecular weights (M, up to 4.4 x 10(4) Da) in high isolation yields (up to 97%). The polymers possessed outstanding thermal stability and emitted strong deep blue light of; 400 nm when their solutions were photoexcited. The polymers effectively limited the light of a 532 nm laser, with the performance of 2 being better than that Of C-60, a well-known optical limiter, under similar linear transmittance.